Switching power supplies are widely used for high power applications because of their high efficiency and small size. Multiphase buck converters are particularly well suited for providing high current at low voltages required by state of the art high performance integrated circuits such as microprocessors, graphics processors, and network processors. Buck converters are typically implemented with active components such as a pulse width modulation controller (PWM), driver, power MOSFETs (metal oxide semiconductor field effect transistors), and passive components such as inductors, transformers or coupled inductors, capacitors, and resistors.
Multiphase buck converters are typically designed so that the elements of each phase (channel) are similar or identical and operated in an interleaved manner to minimize output ripple and provide fastest dynamic response. Buck converters typically operate over a large range of output current, for example from zero to maximum load, and therefore conventional buck converters are not necessarily optimized at any given range. Instead, the designer is restricted in the selection of components and switching frequency to optimize diverse performance parameters such as light load efficiency and fast response to a maximum load step.
For example, multiphase buck converters for microprocessors or other high performance integrated circuits require large amounts of supply current and are subject to very fast transients. Conventional multiphase buck converters typically include many phases (channels) connected in parallel and phase interleaved to equally share and provide high output current so that the regulator can respond quickly to fast dynamic voltage transitions and fast transient load conditions. ‘Fast dynamic voltage transitions’ and ‘fast transient load conditions’ are referred to collectively herein as ‘fast dynamic conditions’. To cope with fast transients, a relatively high switching rate is required. However, high switching frequency yields an inefficient system. The usual solution for obtaining the desired efficiency is to reduce the switching frequency, increase the output capacitor and use several channels in parallel which leads to an increased system cost.